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Statistical concepts, such as the margin of error in a public opinion poll or the probability of rain or snow, appear in everyday conversation. But, just as one may understand how the heart ...
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Statistical concepts, such as the margin of error in a public opinion poll or the probability of rain or snow, appear in everyday conversation. But, just as one may understand how the heart functions and how blood circulates but not be able to perform a cardiac catheterization, an understanding of statistical concepts does not enable one to perform the work of a statistician. Although the concepts may be familiar, the tools of statistics may be misapplied and the results misinterpreted without a statistician’s help. In medical research, the quality of the statistical analysis and clarity of presentation of statistical results are critical to a study’s validity. Decisions about statistical analysis are best made at the time that the study is designed and generally should not be deferred until after the data have been collected. Even the most sophisticated statistical analysis cannot salvage a fundamentally flawed study. Regardless of the statistician’s role, authors (who may include statisticians) are responsible for the appropriate design, analysis, and presentation of the study’s results...Less

Margaret A. Winker and Stephen J. Lurie

Meta-analysis is a systematic pooling of the results of 2 or more studies to address a question of interest or hypothesis. According to Moher and Olkin, [Meta-analyses] provide a systematic and ...
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Meta-analysis is a systematic pooling of the results of 2 or more studies to address a question of interest or hypothesis. According to Moher and Olkin, [Meta-analyses] provide a systematic and explicit method for synthesizing evidence, a quantitative overall estimate (and confidence intervals) derived from the individual studies, and early evidence as to the effectiveness of treatments, thus reducing the need for continued study. They also can address questions in specific subgroups that individual studies may not have examined. A meta-analysis quantitatively summarizes the evidence regarding a treatment, procedure, or association. It is a more statistically powerful test of the Less

Margaret A. Winker and Stephen J. Lurie

In an observational study, the researcher identifies a condition or outcome of interest and then measures factors that may be related to that outcome. Although observational studies cannot lead to ...
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In an observational study, the researcher identifies a condition or outcome of interest and then measures factors that may be related to that outcome. Although observational studies cannot lead to strong causal inferences, they may nonetheless suggest certain causal hypotheses. To infer causation in observational studies, investigators attempt to establish a sequence of events if event A generally precedes event B in time, then it is possible that A may be responsible for causing B. Such studies may be either (the investigator tries to reconstruct what happened in the past) or prospective (the investigator identifies a group of individuals and Less

Margaret A. Winker and Stephen J. Lurie

Although a treatment or screening technique may be shown to be effective in an RCT, recommending it in general practice would not necessarily be rational. Such interventions may be prohibitively ...
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Although a treatment or screening technique may be shown to be effective in an RCT, recommending it in general practice would not necessarily be rational. Such interventions may be prohibitively expensive, or they may benefit only a small number of people at the expense of a large number of people, or they may lead to significant “downstream” costs that would eventually negate any immediate savings or benefit. Thus, it is possible that interventions that appear less effective may actually lead to the greatest societal benefits over the long term. Cost-effectiveness and cost-benefit analyses comprise a set of mathematical techniques to Less

Margaret A. Winker and Stephen J. Lurie

When numbers are expressed in scientific and biomedical articles, they should reflect the degree of accuracy of the original measurement. Numbers obtained from mathematical calculations should be ...
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When numbers are expressed in scientific and biomedical articles, they should reflect the degree of accuracy of the original measurement. Numbers obtained from mathematical calculations should be rounded to reflect the original degree of precision. | The use of a numeral in a numbers column (eg, the ones column) implies that the method of measurement is accurate to that level of precision. For example, when a reporter attempts to estimate the size of a crowd, the estimate might be to the nearest tens of number of people, but would not be expressed as an exact number, such as 86, unless Less

Margaret A. Winker and Stephen J. Lurie

UPDATE: We will discontinue using quotation marks to identify parts of an article, but retain the capitalization; eg, This is discussed in the Methods section (not the “Methods” section). This change ...
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UPDATE: We will discontinue using quotation marks to identify parts of an article, but retain the capitalization; eg, This is discussed in the Methods section (not the “Methods” section). This change was made February 14, 2013. The Methods section should include enough information to enable a knowledgeable reader to replicate the study and, given the original data, verify the reported results. Components should include as many of the following as are applicable to the study design: ▪ Study design (see sections ). ▪ Year(s) (and exact dates if appropriate) when the study was conducted. ▪ Disease or condition to be Less

Margaret A. Winker and Stephen J. Lurie

UPDATE: We will discontinue using quotation marks to identify parts of an article, but retain the capitalization; eg, This is discussed in the Methods section (not the “Methods” section). This change ...
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UPDATE: We will discontinue using quotation marks to identify parts of an article, but retain the capitalization; eg, This is discussed in the Methods section (not the “Methods” section). This change was made February 14, 2013. The Results section should include the number of individuals or other data units initially eligible for study, the number at its inception, and the number who were excluded, dropped out, or were lost to follow-up at each point in the study. For example, JAMA requires a figure showing the flow of participants through controlled trials (see , Randomized Controlled Trials). Authors should provide descriptive Less

Margaret A. Winker and Stephen J. Lurie

In a crossover trial, participants receive more than 1 of the treatments under investigation, usually in a randomly determined sequence, and with a prespecified amount of time (a ) between sequential ...
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In a crossover trial, participants receive more than 1 of the treatments under investigation, usually in a randomly determined sequence, and with a prespecified amount of time (a ) between sequential treatments. The participants and the investigators are generally to the treatment assignment (double-blinded). This experimental design is often used for evaluating drug treatments. Each participant serves as his or her own control, thereby eliminating variability when comparing treatment effects and reducing the sample size needed to detect a effect. Most considerations of parallel-design randomized trials apply. Rather than indicating which participants were assigned to which condition, the CONSORT flow Less

AMA Manual of Style Committee

In this study design, participants are assigned to only 1 treatment group of the study. These trials are generally designed to assess whether 1 or more treatments are superior to the others. ...
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In this study design, participants are assigned to only 1 treatment group of the study. These trials are generally designed to assess whether 1 or more treatments are superior to the others. Participants and those administering the intervention should all be unaware of which intervention individual participants are receiving (“double-blinding”). Ideally, those rating the outcomes should also be blinded to treatment assignment (“triple-blinding”). Blinded parallel-design trials are often the optimal design to compare 2 or more types of drug or other therapy, since known and unknown potentially confounding factors should be randomly distributed between intervention and control groups. The CONSORT Less

Margaret A. Winker and Stephen J. Lurie

It is sometimes desirable to compare a less expensive treatment or intervention against a treatment or intervention that is already known to be effective. In these cases, it would be unethical to ...
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It is sometimes desirable to compare a less expensive treatment or intervention against a treatment or intervention that is already known to be effective. In these cases, it would be unethical to expose participants to an inactive placebo. Thus, these trial designs assess whether the treatment or intervention under study (the “new intervention”) is no worse than an existing alternative (the “active control”). In equivalence and noninferiority trials, authors must prespecify a margin of noninferiority (Δ), within which the new intervention can be assumed to be no worse than the active control. There are a number of methods for arriving Less